A person exerts a horizontal force of 500 N on a box, which also experiences a frictional force of 100 N.
How much work is done against friction when the box moves a horizontal distance of 3 m?
(A) 300 J
(B) 1200 J
(C) 1500 J
(D) 1800 J
(500-400) multiply by 3=1200